The deepening crisis in Ukraine is likely to dominate an summit of European Union leaders in Brussels on Saturday.
EU officials say the leaders of the 28-member bloc will send a clear message to Russia to de-escalate the crisis.
This comes as Ukraine is calling for full membership in NATO, its strongest plea yet for Western military help, after accusing Russia of sending armored columns into eastern Ukraine.
Russian President Vladimir Putin on Friday warned Western nations to avoid "messing" with Russia, pointing out that it's a nuclear-armed power.
NATO is also reportedly considering a new rapid reaction force to boost the military bloc's defenses in response to the crisis.
NATO Secretary-General Anders Fogh Rasmussen is called on Russia to "take immediate and verifiable steps towards de-escalation".